One study of more than 3,200 Hispanic women found being overweight or obese increased the risk for estrogen receptor-negative and progesterone receptor-positive breast tumors among postmenopausal women.

"We've known this for a long time for white women, but now we are seeing this also in Hispanic women," study author Esther John, a senior research scientist at the Cancer Prevention Institute of California, said in an American Institute for Cancer Research news release.

The study was presented Thursday at the research institute's annual meeting in Washington, D.C., and published Oct. 30 in the journal Cancer Epidemiology, Biomarkers & Prevention.

"Breast cancer appears to have different risk factors in younger versus older women but by far, breast cancer is more common among postmenopausal women," John said.

"This has huge implications for not just Hispanics but all women. We cannot change genetics or family history, but we can do something about obesity," she said. "You can eat less, choose healthier foods and do more physical activity. It may not be that easy but it's possible. And it's important for not just lowering breast cancer risk but for many other diseases."

The other study included more than 15,000 black women and found that being overweight or obese increased postmenopausal women's risk of ER-positive breast cancer by 31 percent. It also found that the risk was nearly double among black women who were lean as young adults and gained weight in adulthood.

The study was also released at the cancer research meeting.

"We know that breast cancer has several subtypes and there is growing evidence that these subtypes have different risk factors," study author Dr. Elisa Bandera, of Rutgers Cancer Institute of New Jersey, said in the news release. "The distribution of these subtypes and risk factors are different for African Americans and Hispanics compared to white women."

One study is not enough, said Bandera. "We need to know more about what African American women can do to prevent and survive breast cancers of all types, which are often aggressive and deadly."

More than one in two black women and nearly one in two Hispanic women in the United States are obese.